1. Technical Field
The present invention relates to power supply management in a network workstation, more specifically to power up management arrangements enabling a host computer to be powered up in response to prescribed data packets received by a network interface.
2. Description of the Related Art
Workstation computers are currently being designed to include power saving mechanisms, where the workstation computer will shut itself down after a prescribed interval of activity. The workstation computer is designed to have multiple power supply domains, where a network interface within the workstation will remain in an operative state even though the host computer powers down into a standby state, enabling the network interface to maintain a wake-up routine for the workstation computer.
Specifically, one proposal for a power saving mechanism specifies a wake-up routine for the workstation computer, where a network interface connected to a network such as an Ethernet-type or IEEE 802.3 network maintains sufficient power to receive data packets from a network. For example, one power management scheme developed by Microsoft Corporation, referred to as the "On-Now" Power Management Scheme, enables a network station in a peer-to-peer network to start communication with a destination station, even if the destination station is in a standby condition. According to the On-Now Power Management Scheme, while the rest of the machine is in a low-power state, the network interface in the destination station is monitoring normal network traffic looking for certain classes of frames. When the network interface detects one of these frames, it outputs a signal to initiate CPU operations to control the communications. Additional details related to the "On-Now" power management scheme are described in the Advanced Configuration and Power Interface Specification co-authored by Intel Corporation, Microsoft Corporation, and Toshiba Corporation, dated Dec. 22, 1996 (Rev. 1.0).
An alternative power management scheme is referred to as the Magic Packet.TM., where the network interface scans incoming data frames for one of two MAC addresses repeated sixteen (16) times within the information field of the frames. Hence, the Magic Packet.TM. scheme is more simple because the associated logic is only looking for a prescribed pattern within the data packets.
One concern with the existing on-now power management schemes is that the peripheral component interconnect (PCI) specification has been updated to include a PCI power configuration register that includes a power management enable status (PME.sub.-- STATUS) bit and a PME enable (PME.sub.-- EN) bit. The PME.sub.-- STATUS bit indicates a status in detecting a data packet under the on-now power management scheme. The PME.sub.-- EN bit is a control signal set by the operating system of the host computer. Hence, the PME pin signal is asserted on the PCI bus in response to simultaneous assertion of the PME.sub.-- STATUS bit and the PME.sub.-- EN bit.
Hence, the existing power management schemes rely on the operating system to set the PME.sub.-- EN bit. If power is lost in an on-now system, the CPU needs to be awakened upon return of the power supply in order to reinitialize the on-now power management schemes and the network interface states into a prescribed state. Hence, a substantial problem may exist in legacy systems that do not support OS-directed power management architectures, since the PME.sub.-- EN bit may come up disabled or enabled following a power loss, requiring a complete reset of the workstation.